WLAN: WCN1314: Fixed kernel panic during unloading WLAN driver

Declaring completion variables, card_rem_event_var and shutdown_event_var
as global variables, because we observed these completion variables,
getting freed while wait on these variables.

CRs-Fixed: 393414
Change-Id: Iccc3595d96da8720ea75e869eb1a1d097f594146
Signed-off-by: c_gowri <deepthi@codeaurora.org>